/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.util;

import java.util.HashMap;

import org.apache.tomcat.util.digester.Digester;
import org.xml.sax.InputSource;
import org.xml.sax.EntityResolver;
import org.xml.sax.SAXException;

/**
 * This class implements a local SAX's <code>EntityResolver</code>. All DTDs and
 * schemas used to validate the web.xml file will re-directed to a local file
 * stored in the servlet-api.jar and jsp-api.jar.
 * 
 * @author Jean-Francois Arcand
 */
public class SchemaResolver implements EntityResolver {

	/**
	 * The disgester instance for which this class is the entity resolver.
	 */
	protected Digester digester;

	/**
	 * The URLs of dtds and schemas that have been registered, keyed by the
	 * public identifier that corresponds.
	 */
	protected HashMap entityValidator = new HashMap();

	/**
	 * The public identifier of the DTD we are currently parsing under (if any).
	 */
	protected String publicId = null;

	/**
	 * Extension to make the difference between DTD and Schema.
	 */
	protected String schemaExtension = "xsd";

	/**
	 * Create a new <code>EntityResolver</code> that will redirect all remote
	 * dtds and schema to a locat destination.
	 * 
	 * @param digester
	 *            The digester instance.
	 */
	public SchemaResolver(Digester digester) {
		this.digester = digester;
	}

	/**
	 * Register the specified DTD/Schema URL for the specified public
	 * identifier. This must be called before the first call to
	 * <code>parse()</code>.
	 * 
	 * When adding a schema file (*.xsd), only the name of the file will get
	 * added. If two schemas with the same name are added, only the last one
	 * will be stored.
	 * 
	 * @param publicId
	 *            Public identifier of the DTD to be resolved
	 * @param entityURL
	 *            The URL to use for reading this DTD
	 */
	public void register(String publicId, String entityURL) {
		String key = publicId;
		if (publicId.indexOf(schemaExtension) != -1)
			key = publicId.substring(publicId.lastIndexOf('/') + 1);
		entityValidator.put(key, entityURL);
	}

	/**
	 * Resolve the requested external entity.
	 * 
	 * @param publicId
	 *            The public identifier of the entity being referenced
	 * @param systemId
	 *            The system identifier of the entity being referenced
	 * 
	 * @exception SAXException
	 *                if a parsing exception occurs
	 * 
	 */
	public InputSource resolveEntity(String publicId, String systemId)
			throws SAXException {

		if (publicId != null) {
			this.publicId = publicId;
			digester.setPublicId(publicId);
		}

		// Has this system identifier been registered?
		String entityURL = null;
		if (publicId != null) {
			entityURL = (String) entityValidator.get(publicId);
		}

		// Redirect the schema location to a local destination
		String key = null;
		if (entityURL == null && systemId != null) {
			key = systemId.substring(systemId.lastIndexOf('/') + 1);
			entityURL = (String) entityValidator.get(key);
		}

		if (entityURL == null) {
			return (null);
		}

		try {
			return (new InputSource(entityURL));
		} catch (Exception e) {
			throw new SAXException(e);
		}

	}

}
